1. Field of the Invention
The present invention relates to an antenna device for an automobile. More particularly, it relates to such device useful for an automobile mounting a TV receiver.
2. Description of Prior Art
A glass antenna system in which antenna strips arranged in a desired pattern are provided in a window glass of an automobile has been widely used as an antenna device for an automobile. The antenna device of this kind is tuned in to AM and FM broadcast wave bands so that excellent sensitivity is given to receive radio broadcast waves.
For a television to be mounted on an automobile, which has come recently, there has been a demand of receiving TV broadcast waves by an antenna device for inclusive use for a radio receiver. It was, however, impossible to receive the TV broadcast waves since the conventional antenna device was tuned in to only the radio broadcast waves. Accordingly, an antenna device for inclusive use for a television was required for a TV receiver to be mounted on an automobile in addition to a radio receiver.
Heretofore, there has been proposed an antenna device for inclusive use for the television receiver having such construction that a plurality of rod-like antenna elements are attached to the roof of an automobile to receive TV broadcast waves in a broad band region.
However, the proposed antenna device had such problems that the antenna elements on the car roof constitute external projections which were dangerous to foot passengers and they produced a blowing sound during high-speed running. Further, the antenna elements were easily touched by others at a parking time and easily came into contact with the ceiling of a garage or trees to result in breakage of the antennas.
To resolve the above-mentioned problems, it can be considered that an antenna strip for receiving the TV broadcast waves is installed in a rear window panel made of glass or a resinous material. However, the rear window panel is generally provided with heating strips for defrosting to keep the backward sight clear when it is cold. In this case, it is necessary to arrange the antenna strip in the rear window panel without causing interference by the heating strips.
The rear window panel is required to give clear backward sight. In addition, it is undesirable that both the heating strips and the antenna strip for the TV broadcast waves are installed in the rear window panel from the viewpoint of its appearance. Even though the antenna strip for the TV broadcast waves is disposed in the rear window panel, a space for the heating strips is limited whereby a sufficient by clear backward sight can not be provided when it is cold. This inevitably causes limitation of a space for arrangement of the antenna strip.
On the other hand, for an antenna for the TV receiver, a fairly large space is required in order to give good sensitivity of receiving the TV broadcast waves.
Accordingly, the limited space for the antenna makes maintenance of the excellent radio wave receiving function difficult. Further, in the automobile having the rear window panel in which an antenna strip for receiving radio broadcast waves is installed, it is practically impossible to add the antenna for the TV broadcast waves in the rear window panel.